The present invention relates generally to teat cup assemblies for vacuum-operated automatic milking machines for milking dairy cows. More particularly, the invention relates to an improved teat cup configured for manufacturability and long service life.
Conventional automatic milking machines have been known for many decades. Such machines typically utilize teat cup assemblies for withdrawing milk through each of the cow's teats during milking. A typical teat cup includes a hollow, rigid outer shell or sleeve having a port which is adapted to be attached to a pulsating vacuum line. A resilient, tubular liner or inflation typically extends from a top to a bottom of the sleeve, concentrically disposed within the shell. The ends of the inflation make sealing engagement with the shell to form an annular vacuum chamber between the shell and the inflation. The pressure in the annular chamber is alternated between a lower pressure, typically a sub-atmospheric pressure, and a higher pressure, typically atmospheric, by the pulsating vacuum line attached to the shell at the port. A milk-collecting vacuum line is connected to a milk-receiving cup attached to the shell and in communication with the interior of the inflation, positioned at the lower end of the inflation. This line is to draw milk from the cow's teat and convey it to a collection tank, typically. A cow's teat is received through an upper end of the inflation. The interior of the inflation is, thus, maintained at a sub-atmospheric pressure, and the alternating pressure in the annular chamber periodically forces the walls of the inflation outwardly and inwardly resulting in a massaging action on the teat as well as periodically collapsing the walls of the inflation below the teat. The collapse of the inflation periodically relieves the teat from exposure to the vacuum within the inflation due to the negative pressure in the milk-collecting vacuum line. The teat cup is made heavy enough that it draws the teat downward, and the combination of the effects of the weight of the teat cup and the variation of geometry of the inflation and variation of the amount of vacuum to which the teat is exposed, causes the inflation to ride up and down on the teat by a small amount. All these together help to cause the milk let-down response and improved milk production during milking of the animal.
Inflations are typically composed of elastomeric, resilient, materials due to the need for an inflation to have the properties of such materials, i.e., their capability of recovering to their original size and shape after repeated deformation. Inflations are most often made from a natural rubber or a synthetic rubber composition, e.g. a silicone rubber material. Each of these classes of materials has their own unique advantages and disadvantages. For example, natural rubber compositions are more resistant to tearing or ripping, but are subject to attack by oils, butterfats, teat treatment preparations and other chemicals used in the milking process. On the other hand, synthetic rubber materials such as silicone rubbers can be made substantially less vulnerable to attack by such chemicals. However, silicone rubber tends to crack, tear and puncture more easily than natural rubber. Therefore the configuration of the inflation liner is important to mitigate these service life problems in synthetic rubber materials such as silicone.
It is important that an upper portion of the inflation and/or teat cup as a whole grips the teat firmly to prevent vacuum loss and disengagement of the teat cup from the teat, as well as to prevent the teat cup from moving higher up on the teat during milking due to the up and down motion of the teat cup due to the pulsations of the milking machine. If the teat cup rides up too high, this can ultimately result in constriction of the teat and premature shut off of milk from the udder, even though the udder is not emptied. Moreover, the teats of different cows vary considerably in their diameter and length. Changes in teat sizes also occur during the milking process. These variations and changes make it a challenge to produce “one size fits all” teat cups which can be used in milking a number of different cows. The design of teat cups has generally been toward more complex configurations to maximize advantages and minimize disadvantages in providing the functionality just described.
One approach to a teat cup assembly includes a sphincter-like diaphragm at the upper portion of the assembly which is a separate element made from a molded elastomeric material. Such a diaphragm defines a central opening which maintains sufficient contact with the teat of the cow so as to prevent the teat cup from dropping off the teat, but still sufficiently flexible to be used on teats of various sizes while resisting riding up too high, for example to improve milking efficiency and reduce tissue damage and mastitis, etc. Although the diaphragm provides considerable advantages, the configuration typically requires additional structure to implement. For example one approach is to provide an upper collar and protective cap to sandwich the diaphragm there between This is in turn coupled to an upper portion of the shell, with the inflation disposed within the shell. An example of such a configuration is disclosed in U.S. Pat. No. 4,315,480 to Noorlander.
The additional components of the Noorlander teat cup assembly, as an example of the type, can add to the overall cost. Further, additional components generally translates to greater potential for error in manufacturing; which in can result in greater potential for a failure which can limit the service life of the teat cup.